SYT-SSX Fusion Gene Research Articles

Intraosseous malignant peripheral nerve sheath tumor with focal epithelioid differentiation of the thoracic spine

The authors describe an extremely rare case with malignant peripheral nerve sheath tumor (MPNST) with focal epithelioid differentiation presenting as an intraosseous lesion of the spine. A 75-year-old woman presented with progressive paraplegia caused by epidural mass arising from the posterior element of the T7 vertebra. At surgery, the lesion was noted to originate from the T7 vertebra and separate from the dura and spinal nerve roots. The patient died of tumor metastases to the lungs six months after the initial presentation. Histological diagnosis was MPNST. However, the tumor also contained cystic structures lined by epithelioid cells, requiring differentiation from synovial sarcoma. From the histological and immunohistochemical features, as well as the absence of SYT-SSX fusion gene expression, the diagnosis of MPNST with focal epithelioid differentiation was made. This is the first case report of intraosseous MPNST of the spine with a peculiar biphasic appearance.

Tissue microarray profiling of primary and xenotransplanted synovial sarcomas demonstrates the immunophenotypic similarities existing between SYT-SSX fusion gene confirmed, biphasic, and monophasic fibrous variants

This paper discusses the diversity of synovial sarcomas (SSs) [biphasic (BSS), monophasic fibrous (MFSS), and poorly differentiated (PDSS)] and tissue microarray (TMA) evaluation of the immunophenotypic and histological progression of SSs in nude mice using three TMAs comprising 11 primary SSs (8 MFSSs, 2 BSSs, and 1 PDSS) and their xenografts. BSS and MFSS progressively transformed to a similar undifferentiated phenotype with loss of glandular component in the xenografts. Epidermal growth factor receptor and SALL2 were expressed in primary tumors and xenografts. Enhanced bcl-2 and bax expression were noted in xenografts. Ki-67 overexpression in xenografts correlated with high mitotic index. Epithelial membrane antigen (EMA) and cytokeratin AE1/AE3 were detected in all original and xenografted SSs. Hierarchical clustering differentiated original MFSS and BSS, but their xenografts clustered together due to similar immunoexpression profile. Our study demonstrates definite phenotypic variability of BSS and MFSS in the xenografts. Differences in immunoexpression for various markers existed between primary tumor and xenografts but not between subtypes. Hierarchical clustering grouped TMA immunostaining data and confirmed immunophenotypic variability; however, it failed to reveal any immunophenotypic differences between SYT-SSX1 and SYT-SSX2 type tumors. Nonetheless, reverse-transcriptase-polymerase chain reaction detected SYT-SSX transcripts in all primary SSs and their xenografts, thereby demonstrating their genetic stability.

Resected case of synovial sarcoma in the pleural cavity

A 29-year-old female was admitted to our hospital complaining of severe dry cough and low-grade fever. A chest roentgenogram and a chest computed tomographic scan revealed a huge tumor and massive pleural effusion in the left pleural cavity. Pathological examination revealed spindle shaped malignant cells. SYT-SSX fusion gene transcripts were detected, so we diagnosed the tumor as a synovial sarcoma in the pleural cavity. After neoadjuvant chemotherapy we resected the tumor completely. A synovial sarcoma in the pleural cavity is extremely rare. To the best of our knowledge, this is the thirteenth case, and the first case to undergo neoadjuvant chemotherapy and complete resection. Because a synovial sarcoma in the pleural cavity has a poor prognosis and is characterized by a high incidence of recurrence, we must carefully follow up this patient.

Molecular Detection of SYT-SSX Fusion Gene Transcripts Currently Represents the Most Specific and Sensitive Tool for Diagnosing Intrathoracic Synovial Sarcoma

Molecular Detection of SYT-SSX Fusion Gene Transcripts Currently Represents the Most Specific and Sensitive Tool for Diagnosing Intrathoracic Synovial Sarcoma

Reverse transcription-polymerase chain reaction in situ hybridization for SYT-SSX fusion gene transcripts in synovial sarcomas.

More than 90% of synovial sarcomas (SSs) possess a non-random chromosomal translocation t(X;18)(p11;q11) and express SYT-SSX fusion gene products originating from the translocation. To test whether it is possible to detect the SYT-SSX mRNA on archival formalin-fixed paraffin-embedded SS tissue sections using PCR-based in situ amplification technique, we performed reverse transcription-polymerase chain reaction in situ hybridization (RT-PCR ISH) for the SYT-SSX fusion gene mRNA. In three types of SSs, monophasic fibrous, biphasic and poorly differentiated, NBT/BCIP signals corresponding to SYT-SSX mRNA were uniformly and predominantly positive in the sarcoma cell cytoplasm. Our results indicated that SS cells uniformly possessed the SYT-SSX fusion genes and expressed their transcripts. Furthermore, our results were thought to support monoclonal origin of epithelial and spindle cell components of biphasic SSs. Thus, specific chromosomal translocation t(X;18) is likely to be an early event in the development of SSs, and the expression of SYT-SSX fusion gene products is thought to be crucial for the tumorigenesis of SSs.

Epithelioid sarcoma with SYT-SSX1 fusion gene expression: molecular and cytogenetic analysis

Epithelioid sarcoma is a rare malignant soft tissue tumor of unknown histogenesis, characterized by the epithelioid morphology of tumor cells and co-expression of epithelial and mesenchymal lineage proteins. A common epithelial and mesenchymal immunophenotype is also found in another soft tissue tumor, the biphasic subtype of synovial sarcoma. Furthermore, the presence of a breakpoint at 18q11 in epithelioid sarcoma, similar to that found in synovial sarcoma, has been reported. These facts would support the hypothesis that both tumors may share a common histogenetic background. However, expression of the SYT-SSX fusion genes has been investigated in epithelioid sarcoma with negative results. We report, to our knowledge, the first epithelioid sarcoma in which the presence of SYT-SSX1 fusion gene has been detected by means of conventional RT-PCR analysis and sequencing, real-time RT-PCR and FISH. The SYT-SSX1 gene fusion was identified in a small proportion of tumoral cells. This finding supports a likely common histogenetic background for both epithelioid sarcoma and synovial sarcoma.

Mutational Analysis of the c-KIT AND PDGFR?? in a Series of Molecularly Well-Characterized Synovial Sarcomas

The c-KIT and the platelet-derived growth factor receptor alpha (PDGFRalpha) have been shown to be important for tumor growth and progression in several soft-tissue sarcomas, including synovial sarcomas (SSs). It has been suggested that these c-KIT-positive cases might benefit from a tyrosine kinase inhibitor therapy. In this study, we analyze a series of SSs to investigate the presence of c-KIT and PDGFRalpha mutations with the aim of selecting those for a more adequate and appropriate therapy. We analyzed fresh-frozen tissues from 12 SSs (8 primary tumors and 4 nude mice xenotransplants from primary tumors). RNA was extracted to identify the presence of the SYT-SSX gene fusion to confirm the SS diagnosis. Mutational analysis of exons 9, 11, 13, and 17 of c-KIT and exons 12 and 18 of PDGFRalpha was performed by direct sequencing. Immunohistochemical analysis of c-KIT, PDGFRalpha, and p-PDGFRalpha was also performed. All analyzed cases showed the presence of SYT-SSX gene fusion transcripts confirming the diagnosis of SS, 10 carried the SYT-SSX1 fusion, and 2 the SYT-SSX2. Immunohistochemical analysis showed expression of c-KIT in 3 cases in which no molecular alterations were detected. For the PDGFRalpha, we observed an in-frame deletion of codons 554 and 555 in a case which also showed a strong immunopositivity for the phosphorylated form of PDGFRalpha. PDGFRalpha expression was observed in 8 cases. We suggest that a more exhaustive mutational analysis of the c-KIT and PDGFRalpha genes should be performed to ascertain which cases would really benefit from a tyrosine kinase inhibitor therapy in SS.

A 37-Year-Old Man With a Pleural Mass

A 37-year-old man presented to an outside hospital with a dry cough, progressive dyspnea, and left-sided chest pain of 1 month's duration. Chest radiography and computed tomography showed a large left pleural effusion and a left lung mass without hilar or mediastinal lymphadenopathy. Following thoracentesis of an apparent nonmalignant effusion, thoracoscopic pleural biopsy was performed. The patient was subsequently referred to our hospital, where he underwent thoracotomy with left upper lobectomy and partial pericardiectomy.Gross examination of the resected specimen revealed an 11.0 × 10.0 × 3.5-cm poorly circumscribed pleural tan-white mass with areas of hemorrhage, compressing the left upper lobe of lung and adherent to the pericardium. Multiple additional friable tissue fragments, 20.2 × 16.0 × 7.5 cm in aggregate, were present.Microscopically, the tumor was composed of sheets and long fascicles of densely packed, plump spindle cells with dark staining, oval nuclei, and scant cytoplasm (Figures 1 and 2). The degree of vascularity was variable, with focal hemangiopericytoma-like areas containing numerous dilated vascular spaces. Epithelioid cells, calcifications, or areas of ossification were not observed. Immunohistochemical studies for S100, CD34, keratin, and epithelial membrane antigen were negative. Bcl-2 immunohistochemistry was diffusely positive (Figure 3).Cytogenetic analysis demonstrated a t(X;18)(p11.2;q11.2) balanced reciprocal translocation (Figure 4). Following surgery, the patient was treated with ifosfamide chemotherapy and was alive and well, free of recurrent disease, 9 months after surgery.What is your diagnosis?Synovial sarcoma is a well-described soft tissue neoplasm, most often located in the extremities adjacent to large joints in adolescents and young adults 15 to 40 years of age. Despite its name, the tumor generally shows no association with joint cavities and has been described in numerous nonsynovial locations, including the heart, abdominal wall, parapharyngeal region, mediastinum, and pleural cavity. When these tumors arise from the pleura, patients often present with chest pain and dyspnea. Effusions and pleural-based masses may be noted radiographically. Computed tomographic scans typically demonstrate a soft tissue mass with intratumoral calcifications in 20% to 30% of cases.Gross pathologic examination reveals a localized mass, generally 5 to 20 cm in greatest dimension, consisting of gray-white to tan fleshy soft tissue.12 Hemorrhage, necrosis, cystic degeneration, and calcification are variably present. Similar to the para-articular synovial sarcomas, those in the pleural cavity are often completely or partially invested by a glistening pseudocapsule. In the thoracic cavity, distinction between pleural- and pulmonary-based lesions may be difficult, and tumors may be described as pleuropulmonary.3Microscopically, the tumors are classically composed of a biphasic pattern of epithelial and spindle cells. Monophasic patterns, as illustrated in this case, consist of either the spindle or the epithelial component; the former is more common than the latter. The epithelial cells are cuboidal to columnar, with vesicular nuclei and abundant pale-staining cytoplasm with distinct cellular borders, and are arranged in cords, nests, or glands. The surrounding densely packed sheets of spindle cells have plump, dark-staining nuclei with indistinct cytoplasm, often arranged in long, interweaving fascicles. Nuclear palisading in the spindle cell areas may be evident. Myxoid change, calcifications, and mast cells are variably present.Immunohistochemically, most synovial sarcomas display at least focal immunoreactivity for cytokeratin and epithelial membrane antigen, which is usually more prominent in the epithelial component. Multiple sections may need to be examined to identify positivity in the spindle cell areas, and even so, our case was negative for both stains. CD99 and Bcl-2 are also detected in the majority of cases. Synovial sarcomas are negative for CD34.The differential diagnosis of a spindle cell neoplasm in the pleural cavity includes sarcomatoid malignant mesothelioma,45 solitary fibrous tumor, hemangiopericytoma, and sarcomatoid carcinoma. Malignant mesotheliomas usually present in patients of older age (50–70 years) with antecedent asbestos exposure, and they diffusely involve the pleural cavity. Solitary fibrous tumor and hemangiopericytoma consistently express CD34, whereas synovial sarcoma does not. Other entities, such as fibrosarcoma, leiomyosarcoma, and malignant peripheral nerve sheath tumor, may share histologic similarities, but these are rare primary tumors of the pleural cavity, distinguishable by immunohistochemistry. In addition, because synovial sarcoma preferentially metastasizes to the lung, an extrathoracic primary origin should be ruled out.The chromosomal translocation t(X;18)(p11.2;q11.2), which has been identified in more than 90% of synovial sarcomas, results in an SYT-SSX gene fusion.67 Detection of this translocation by conventional cytogenetics, fluorescence in situ hybridization, or reverse transcriptase polymerase chain reaction8 is helpful in establishing the diagnosis, particularly in monophasic variants.9Treatment for synovial sarcoma has included surgical resection, chemotherapy, and radiation. Favorable prognostic factors include a tumor size less than 5 cm, low mitotic rate (<10 mitotic figures per 10 high-power fields), absence of necrosis, and local eradication. Metastases occur in approximately half of the cases, and these may be noted many years following the initial diagnosis. Five-and 10-year survival rates range from 36% to 76% and 20% to 63%, respectively.10

Primary Pulmonary Synovial Sarcoma Confirmed by Molecular Detection of SYT-SSX1 Fusion Gene Transcripts: a Case Report and Review of the Literature

This is a case report of a rare patient with primary pulmonary synovial sarcoma. The patient was a 58-year-old woman who presented with a well-defined giant mass in the right lower field on a chest radiograph. A malignant pulmonary tumor was suspected and consequently a right middle and lower lobectomy was performed. Grossly, the tumor measured 10 x 8 x 7 cm, was whitish-yellow in color and friable with hemorrhage. Histologically, the tumor showed a dense proliferation of spindle cells. In some areas, a herringbone-like pattern with coagulation necrosis of large size was noted. Immunohistochemically, the tumor cells were focally positive for cytokeratin and epithelial membrane antigen (EMA). As these features suggested a monophasic synovial sarcoma, we looked for the presence of SYT-SSX fusion gene transcripts using RNA samples from the paraffin-embedded tissue. A reverse transcription-polymerase chain reaction (RT-PCR) amplified a single 118 bp fragment characteristic of the SYT-SSX1 fusion gene transcripts. As no tumor was found at other sites, it was diagnosed as primary pulmonary synovial sarcoma. Molecular testing proved to be very helpful or necessary when monophasic spindle cell synovial sarcoma was recognized in uncommon/unexpected sites. In our review of primary pulmonary synovial sarcomas confirmed by molecular detection of SYT-SSX fusion gene transcripts, the SYT-SSX2 fusion protein expression correlates with poorer prognosis. This is in contrast to the association between the SYT-SSX1 fusion protein expression and poorer prognosis in soft tissue synovial sarcomas.

Thoracic-Abdominal Approach in Primary Pulmonary Synovial Sarcoma

We report a case of primary synovial sarcoma of the lung. The patient was a 32-year-old male who presented with a mass in the right hemithorax invading the peritoneal cavity. The neoplasm was resected through a thoracic-abdominal approach. The patient is doing well 21 months after surgery. Within the last decade thoracic localizations of synovial sarcoma are an emerging histopathological entity thanks to the molecular analysis of the SYT-SSX fusion gene transcript.

Primary Renal Synovial Sarcoma Confirmed by Cytogenetic Analysis: A Lesion Distinct From Sarcomatoid Renal Cell Carcinoma

Primary synovial sarcoma rarely originates in the renal parenchyma. When this occurs, origin of this unusual tumor type has been the subject of debate in the literature, with a suggestion that previously reported cases may be more correctly described as renal cell carcinoma with sarcomatoid dedifferentiation. Synovial sarcoma and sarcomatoid renal cell carcinoma may be indistinguishable on pure histologic and immunohistochemical grounds, but these tumors contain distinctly different sets of chromosomal abnormalities. Most previous cases of primary renal synovial sarcoma were confirmed by molecular biology techniques, which detected the SYT-SSX gene fusion transcript typical of this tumor, but no details of the other chromosomal anomalies have been published. We report a case of primary renal synovial sarcoma confirmed by standard cytogenetic analysis, showing the characteristic t(X; 18)(p11.2:q11.2) translocation and other chromosomal aberrations that are typical of synovial sarcoma as opposed to sarcomatoid renal cell carcinoma.

Phase I vaccination trial of SYT-SSX junction peptide in patients with disseminated synovial sarcoma

BackgroundSynovial sarcoma is a high-grade malignant tumor of soft tissue, characterized by the specific chromosomal translocation t(X;18), and its resultant SYT-SSX fusion gene. Despite intensive multimodality therapy, the majority of metastatic or relapsed diseases still remain incurable, thus suggesting a need for new therapeutic options. We previously demonstrated the antigenicity of SYT-SSX gene-derived peptides by in vitro analyses. The present study was designed to evaluate in vivo immunological property of a SYT-SSX junction peptide in selected patients with synovial sarcoma.MethodsA 9-mer peptide (SYT-SSX B: GYDQIMPKK) spanning the SYT-SSX fusion region was synthesized. Eligible patients were those (i) who have histologically and genetically confirmed, unresectable synovial sarcoma (SYT-SSX1 or SYT-SSX2 positive), (ii) HLA-A*2402 positive, (iii) between 20 and 70 years old, (iv) ECOG performance status between 0 and 3, and (v) who gave informed consent. Vaccinations with SYT-SSX B peptide (0.1 mg or 1.0 mg) were given subcutaneously six times at 14-day intervals. These patients were evaluated for DTH skin test, adverse events, tumor size, tetramer staining, and peptide-specific CTL induction.ResultsA total of 16 vaccinations were carried out in six patients. The results were (i) no serious adverse effects or DTH reactions, (ii) suppression of tumor progression in one patient, (iii) increases in the frequency of peptide-specific CTLs in three patients and a decrease in one patient, and (iv) successful induction of peptide-specific CTLs from four patients.ConclusionsOur findings indicate the safety of the SYT-SSX junction peptide in the use of vaccination and also give support to the property of the peptide to evoke in vivo immunological responses. Modification of both the peptide itself and the related protocol is required to further improve the therapeutic efficacy.

SYT, a partner of SYT-SSX oncoprotein in synovial sarcomas, interacts with mSin3A, a component of histone deacetylase complex

Synovial sarcomas are soft-tissue tumors predominantly affecting children and young adults. They are molecular-genetically characterized by the SYT-SSX fusion gene generated from chromosomal translocation t(X; 18) (p11.2; q11.2). When we screened new gene products that interact with SYT or SSX proteins by yeast two-hybrid assay, we found that mSin3A, a component of the histone deacetylase complex, interacts with SYT but not with SSX. These results were confirmed by mammalian two-hybrid and pull-down assays. Analyses with sequential truncated proteins revealed a main mSin3A-interaction region on the SYT amino-terminal 93 amino acids, and another one on the region between 187th amino acid and break point. In luciferase assay, mSin3A repressed the transcriptional activity of reporter promoter mediated by SYT and hBRM/BRG1. Our results suggest that the histone deacetylase complex containing mSin3A may regulate the transcriptional activation mediated by SYT.

Primary pulmonary synovial sarcoma: a clinicopathologic, immunohistochemical, and molecular study of 11 cases

Primary synovial sarcoma (SS) of the lung is rare and may create diagnostic challenges. We reviewed 11 cases of pulmonary SS (PSS) confirmed by the presence of a tumor-specific SYT-SSX fusion gene to verify their clinicopathologic features including immunohistochemical and genetical profiles. The tumors occurred in 4 men and 7 women (age 29 to 81 years; mean age, 58; median age, 50), and ranged in size from 2 to 15.5 cm (mean, 9 cm). Of the 11 tumors, 10 were a monophasic fibrous type and 1 was a poorly differentiated type. Mitotic rate ranged from 8 to 43 per 10 high-power fields. All cases showed at least focal immunohistochemical positivity for AE1/AE3, CAM5.2 and/or epithelial membrane antigen. High proliferating cell nuclear antigen labeling index (>20%) was found in 8 of 10 cases (80%). Eight (90%) of 9 cases were negative for E-cadherin, and 1 case (10%) exhibited reduced expression of the molecule. The aberrant expression of β-catenin within cytoplasm and/or nuclei was observed in 6 of 9 (67%) cases. SYT-SSX1 and SYT-SSX2 fusion gene transcripts were detected in 9 and 2 cases, respectively. In 10 patients with follow-up, 3 (30%) had local recurrences, and 4 (40%) developed distant metastases. Five (50%) patients died of the tumor 1 to 9 years after surgery, and 5 (50%) were alive and disease-free in the period ranging from 3 months to 5.5 years. In conclusion, PSS tends to occur in older patients and shows an aggressive behavior probably due to its anatomical location and large tumor often resulting in incomplete resection and high proliferative activity.

Synovial sarcoma metastatic to stomach and duodenum

A 49-year-old Japanese man presented witha painful mass on his right calf that was foundby histopathologic and immunohistochemical anal-yses of an open biopsy specimen to be a synovialsarcoma of the monophasic fibrous type. An SYT-SSX1 fusion gene, resulting from the chromosomaltranslocation of t(x;18)(p11.2;q11.2) was detected byreverse transcription polymerase chain reaction.After amputation of his right leg, the patientunderwent chemotherapy and radiotherapy to treatlung metastases. Subsequently, he developed me-lena and was found to be anemic. Upper endoscopydemonstrated multiple protruding lesions with acentral depression in the stomach and duodenum(A,B,C).Freshclotwasattachedtooneofthelesions.Biopsy specimens from one of the gastric lesionsrevealed spindle cell proliferation in the mucosa(D, H&E, orig. mag. 333) that was similar to thesynovial sarcoma from the right calf.

Gene expression profile by blocking the SYT-SSX fusion gene in synovial sarcoma cells. Identification of XRCC4 as a putative SYT-SSX target gene.

Increasing evidence suggests that the SYT-SSX fusion gene plays an important role in synovial sarcoma development and progression. However, very little is known about the downstream targets of SYT-SSX. In this study, we used antisense oligonucleotides to block the expression of the SYT-SSX fusion gene in synovial sarcoma cells. By comparing SYT-SSX inhibited cells with noninhibited cells, the gene expression profile was analysed using cDNA microarray and established by real-time PCR. Herewith, using a filter containing 1176 cancer-relevant genes, we found that the DNA repair gene XRCC4 and the DNA mismatch repair gene MSH2 were downregulated, whereas the gene encoding for the serine/threonine protein kinase PRK (also known as CNK), and the macrophage inhibitory cytokine MICI (also known as PLAB) were upregulated after the inhibition of SYT-SSX. In comparison, expression of the XRCC4 gene was undergoing the strongest alteration. Consistently, the protein expression of XRCC4 was found to be decreased after SYT-SSX inhibition, whereas there were no detectable changes for the other gene products. Our study provides some clues to elucidate the signaling pathways of the SYT-SSX fusion gene, as well as it demonstrates a valuable model system for search for other SYT-SSX targets.

Synovial Sarcoma with Massive Ossification – A Case Report

Synovial sarcoma with extensive osteoid production is rare. We report a case of synovial sarcoma of monophasic type with massive ossification. The diagnosis was confirmed by reverse-transcripitase polymerase chain reaction (RT-PCR). The patient was an-81-year-old woman with recurrent synovial sarcoma in her right knee. The tumor was primarily excised in 1989. It recurred and was removed again in 1996. However, in 1999 a painful mass appeared in the same site. Preoperative plain radiography and computed tomography revealed a 5 x 5 cm soft tissue mass with extensive ossification in the medial side of the right knee joint. The tumor was widely excised in 2000. Soft X-ray examination revealed a trabecular pattern of ossification in the excised tumor. Microscopically the tumor was composed of hypercellular spindle cells with fascicular arrangement with prominent ossification but no epithelial component. The tumor cells were positive for vimentin and focally positive for cytokeratin. The tumor expressed a sequence of SYT-SSX1 fusion gene transcript demonstrated by RT-PCR. Twelve years long survival of the present case without metastasis in spite of repeated recurrence suggests a better prognosis of synovial sarcomas with ossification.

The SYT-SSX1 fusion type of synovial sarcoma is associated with increased expression of cyclin A and D1. A link between t(X;18)(p11.2; q11.2) and the cell cycle machinery.

A recent large multi-centre study convincingly confirmed previous observations that the SYT-SSX1 fusion type, compared to SYT-SSX2, of synovial sarcoma is associated with a worse clinical outcome. Apart from the clinical impact, this fact also suggests (1) that the SYT-SSX fusion gene may influence molecular mechanisms involved in tumour growth and progression; and (2) that the SYT-SSX1 fusion type has a stronger influence on these mechanisms than SYT-SSX2. The nature of the underlying mechanisms is, however, still unknown. In this study we made use of the SYT-SSX1 vs SYT-SSX2 concept to investigate whether major, tumour relevant, and growth regulatory proteins (e.g. cyclins and cyclin-dependent kinases) may be involved. Using Western blotting analysis on 74 fresh, fusion variant-typed, tumour samples from localized synovial sarcoma, we found a significant correlation between SYT-SSX1 and high expression of cyclin A (P=0.003) and D1 (P=0.025). Our data suggest that SYT-SSX may influence the cell cycle machinery, and that the more aggressive phenotype of the SYT-SSX1 variant is due to an accelerated tumour cell proliferation.

Synovial sarcoma with a secondary chromosome change der(22)t(17;22)(q12;q12)

A consistent, pathognomonic translocation, most commonly a balanced reciprocal translocation, t(X;18) (p11.2;q11.2), is found in more than 90% of synovial sarcomas. We report here a secondary chromosome change, der(22)t(17;22)(q12;q12), in addition to the primary t(X;18)(p11.2;q11.2) in a biphasic synovial sarcoma that occurred in the thigh of a 34-year-old woman. Although the karyotype of the primary tumor exhibited 46,X,t(X;18)(p11.2;q11.2), the recurrent tumor showed 46,X,der(X)t(X;18)(p11.2;q11.2),der(22) t(17;22)(q12;q12). The SYT-SSX1 fusion transcript was demonstrated in the primary and recurrent tumors using a reverse transcriptase polymerase chain reaction (RT-PCR). Southern blot analysis also confirmed that the detected messages were derived from the SYT-SSX fusion gene. However, we could not detect the EWS-E1AF fusion gene that has been reported to be generated through a t(17;22)(q12;q12) by RT-PCR. Furthermore, fluorescence in situ hybridization (FISH) with cosmid probes corresponding to loci flanking the EWSR1 region demonstrated no split of chromosome 22 in all analyzed interphase nuclei. To our knowledge, this is the first reported case of synovial sarcoma in which an additional (secondary) chromosome change, der(22)t(17;22)(q12;q12), has been demonstrated.

Detection and induction of CTLs specific for SYT-SSX-derived peptides in HLA-A24(+) patients with synovial sarcoma.

To investigate the immunogenic property of peptides derived from the synovial sarcoma-specific SYT-SSX fusion gene, we synthesized four peptides according to the binding motif for HLA-A24. The peptides, SS391 (PYGYDQIMPK) and SS393 (GYDQIMPKK), were derived from the breakpoint of SYT-SSX, and SS449a (AWTHRLRER) and SS449b (AWTHRLRERK) were from the SSX region. These peptides were tested for their reactivity with CTL precursors (CTLps) in 16 synovial sarcoma patients using HLA-A24/SYT-SSX peptide tetramers and also for induction of specific CTLs from four HLA-A24(+) synovial sarcoma patients. Tetramer analysis indicated that the increased CTLp frequency to the SYT-SSX was associated with pulmonary metastasis in synovial sarcoma patients (p < 0.03). CTLs were induced from PBLs of two synovial sarcoma patients using the peptide mixture of SS391 and SS393, which lysed HLA-A24(+) synovial sarcoma cells expressing SYT-SSX as well as the peptide-pulsed target cells in an HLA class I-restricted manner. These findings suggest that aberrantly expressed SYT-SSX gene products have primed SYT-SSX-specific CTLps in vivo and increased their frequency in synovial sarcoma patients. The identification of SYT-SSX peptides may offer an opportunity to design peptide-based immunotherapeutic approaches for HLA-A24(+) patients with synovial sarcoma.